The present invention relates to a chuck device of a machine tool and, more particularly, to an inside chuck device adapted to carry a workpiece on an outer periphery thereof.
A collet chuck device is broadly known and used as the inside chuck device of machine tools. This collet chuck device has a collet provided at its one end with a tapered bore and a plurality of axial slits and a tapered shaft adapted to make a sliding fit with the tapered bore. As the tapered shaft is slid into the tapered bore, the end portion of the collet having the axial slits is expanded radially outwardly so that the outer peripheral surface of the collet is pressed against the inner peripheral surface of a bore of a cylindrical workpiece to hold the latter. This collet chuck, however, has various drawbacks. Namely, if the bore of the workpiece is not finished in exactly circular form, it is not possible to obtain a uniform engagement between the collet and the work resulting in an unstable holding of the workpiece. In addition, since the collet itself lacks rigidity, the collet is deflected in the direction perpendicular to the axis of the workpiece to permit a slip between the work and the collet to make the machining difficult.